there's a lot of theories along these lines that can, for someone who really thinks in a similar fashion, come as rather interesting. here's what I've heard, thought up, or seen on TV.
In regards to a big bang,
There was some variant of matter that exists in the voids of space, the REAL voids, not the vacuum, that collided, making the big bang occur, which led to the expansion of the universe,
There are multiple universes, with ours being the only one we can see due to light speed restricting how far we can see yet, in a much bigger universe, which leads to the same inevitable question,
the big bang was one of god's farts. (needless to say, I rolled my eyes and walked away from this particular chat.)
On the subject of existence,
We're a simulation in a super advanced computer by some higher being we'll never truly know, for whatever purpose they may have programmed us for.
We're a simulation by real humans who are hundreds or thousands of years further along in their timeline than we are,
We're actually Dwarf Fortress from the year 2050
On the subject of reality.
Our perception is actually far from reality, though we'll never know it due to how we perceive things,
Our minds are all interconnected on some higher level, leading to our joint perception of reality dictating actual reality. IE, if enough people believe there's a tree or a wall somewhere, there IS a tree or wall somewhere, and visa versa. (one of my personal favorite theories, too.)
we're all actually the result of a Boltzmann brain, (a link for those who want to read more about this one.
http://en.wikipedia.org/wiki/Boltzmann_brain)
and that's it for my contribution.
